Media Access Control (MAC) may enable multiple access for a plurality of nodes to the content within a single node. Several multiple access techniques perform the MAC task to a certain degree. However, each of the current access techniques maintains limitations to throughput as node number increases.
Random access techniques to the single node may employ a “transmit as required” technique such as Random Aloha where throughput greatly decreases with an increasing number of transmitting nodes. A time division access technique such as Time division multiple access (TDMA) may allow multiple users access to a common frequency divided into time slots. A Carrier Sense Multiple Access (CSMA) technique may allow multiple users access to a common node through node verification of open time before transmission.
A Statistical Priority-Based Multiple Access (SPMA) technique may employ an omnidirectional transmitter to transmit a shared signal to a plurality of users. This contingent based statistical protocol may employ a spectrum allocation to enable multiple users' access to the limited spectrum. Instead of being contingent on one channel with multiple packets at a time, SPMA may employ multiple channels using multiple pulses of the same packet of information sent across the multiple channels. These multiple pulses may then be received and processed enabling greater throughput of the signal and message reception.
With traditional SPMA, one technique may employ a receiver continuously staring at each channel associated with a transmitter pseudo randomly alternating across the channels. During transmission, the receiver is blinked allowing send and receive across each of the channels. Received packets are processed to create the message from packets arriving via any of the channels.
As node numbers increase, SPMA may sense the activity in the channel and requires node transmission reduction or “back off” to maintain the channel loading below a given interference level. This technique may allow multiple receiver node access to the common node providing per node throughput that may scale as T/N, where T is the SPMA channel capacity and N is number of nodes in the network. As indicated, with increasing number of nodes N, the per-node throughput decreases proportional to 1/N. Further, the total network throughput may be limited and may scale as T.
Each of these access protocols may allow users multiple access to a common node. However, each of these access protocols is limited in node throughput by the number of nodes requesting access. As a finite level of channel occupancy is exceeded, each of these techniques may either reduce available bandwidth or catastrophically fail.
In the physical layer, many traditional systems employ omnidirectional transmitters associated with omnidirectional receivers to maintain communication between nodes. In this situation, a transmitter node may economically offer its content to the plurality of receive nodes (e.g., transmit 1 receive n) via transmission at one time and receive simultaneously at a different time from n other nodes. As these time differences are small, the transmission and reception may appear to be simultaneous to a user. As small as this time difference may be, the break in receive capability during transmission still remains. Each node within range may require some portion of time to transmit and receive lowering the total throughput of the network. In addition, each of these systems may require 10 parallel receive modems providing a network processing throughput limited to approximately 20 megabits per second (mbps).
Traditional directional transmit and receive systems may require either two frequencies and antennas per link (one transmit, one receive) or one frequency and one antenna per link (TDMA Half duplex). These traditional systems may require two expensive antennas and apertures dedicated to each link and a high latency value. These traditional systems maintain a throughput directly dependent on the number of nodes in the neighborhood and the traffic patterns therein.
Therefore a need remains for a system and related method offering priority based multiple access to omnidirectionally transmit while directionally receiving offering a total network throughput capacity which scales based on the number of nodes in a narrow receive field of view.